Recent research in the hearing sciences has established a new class of auditory responses termed otoacoustic emissions that can be objectively measured in the ear canal of all normally hearing individuals. Based upon this knowledge, it is now possible to develop objective hearing-screening instruments for the assessment of dysfunction based upon the absence of emitted responses. One type of emission elicited by the application of continuous pure tones is called a distortion-product emission (DPE). In comparison to the other emitted responses, DPEs offer a significant advantage in that they can provide a detailed objective "audiogram" within a reasonably short time period. Moreover, DPEs can be measured over a relatively large range of hearing loss. The specific aims of the present application are designed to compress existing laboratory instrumentation for the collection of DPEs into a microcomputer-based clinical device. A portable, easy-to-operate instrument will allow collection of sufficient normative data in a clinical setting so that the device can eventually be refined into a commercial package for routine hearing screening in newborns, infants, children, and adults. Phase I focuses on adapting current general-purpose laboratory software so that it will operate on a Macintosh II microcomputer and replacing current general-purpose laboratory instrumentation with on-board signal-generation and spectral-analysis functions. In addition, special emphasis will be devoted to the development of software-based noise-rejection schemes in order to increase the measurable range of DPEs and to permit emissions t be collected eventually in a quiet clinical setting. The future work of Phase II will aim at refining the basic instrumentation of the prototypical device by the addition of programmable, on-board filters, updating software-user interfaces, and collecting substantial normative data from both normally hearing and hearing-impaired individuals.